An 18 year old boy presented with small genitalia, failure of eruption of secondary sex hairs, female like voice with eunachoid body habitus, bilateral gynecomastia, infantile external genitalia, small testes and poorly developed musculature. He was diagnosed as a case of 47XXY Klinefelter syndrome on the basis of hormone assay and karyotyping. He has given androgen replacement therapy with the aim to relieve symptoms of androgen deficiency, to reproduce physiological levels of plasma testosterone and to prevent long term consequences of androgen deficiency.